1. Field of the Invention
The present invention relates to a power source apparatus for rectifying an A.C. (Alternating Current) voltage supplied from an A.C. power source to generate a stable D.C. (Direct Current) voltage.
2. Description of the Related Art
A power source board used in a game console, a television set or the like is equipped with an A.C.-D.C. power source apparatus for converting a home A.C. input voltage into a D.C. output voltage.
Although there are some kinds of converter systems used in the power source apparatus, a system which is most widely used in the power source requiring an electric power of 100 W or more is a full-wave current resonance system.
When the full-wave current resonance system is used in the power source apparatus, a secondary-side circuit alternately carries out a rectifying operation by using two pairs of rectifying diodes.
In addition, when a loss dissipated in each of the diodes used in the secondary-side circuit is desired to be suppressed, a field effect transistor (FET) is substituted for each of the diodes, and a synchronous rectification operation is carried out by using a driving circuit.
When the synchronous rectification operation is carried out for the secondary-side circuit by utilizing the full-wave current resonance system, a driving method using a tertiary winding is known as a main driving method.
FIG. 1 is a circuit diagram showing an example of a configuration of a power source apparatus utilizing the full-wave current resonance system using a tertiary winding of a secondary-side circuit.
This power source apparatus 1 includes a primary coil L1, a secondary coil L2, a tertiary coil L3, a field effect transistor FET2, and a field effect transistor FET3, and gate drivers GD1 and GD2.
In the power source apparatus 1, the coil L3 is used as a tertiary winding, and a pulse is induced in the tertiary coil L3 so as to correspond to the resonance from the primary side, and gates of the field effect transistors FET2 and FET3 are driven by the gate drivers GD1 and GD2, respectively.